In this work we report on the use of the thermal lens spectrometry to determine the absolute values of thermal diffusivity, thermal conductivity, and temperature coefficient of optical path-length change of several fluoride glasses. The results showed that flouride glasses doped with minor quantities of Ga, In, and Zn exhibit thermal conductivities and thermal diffusivities roughly 20% larger than that of fluorozirconate (ZBLAN) glasses, whereas their temperature coefficients for the optical path-length change was found to be 50% smaller. This suggests that these fluoride glasses may be considered as promising candidates for high power laser applications. We have also demonstrated how this technique can be used for the complete thermo-optical properties characterization as a function of temperature.

In this work, two sets of lead fluoroindogallate glasses were studied with the aim of using them as active media for laser devices at the mid infrared (∼2.8 μm) and visible (∼0.54 μm) regions. The infrared and upconverted emissions of ${\mathrm{Er}}^{\text{3+}}$ in single and ${\mathrm{Er}}^{\text{3+}}:{\mathrm{Yb}}^{\text{3+}}$ codoped samples were analyzed, and it was observed that the best set of samples for 2.8 μm emission was the single doped one, and that as the upconversion (anti-Stokes luminescence) increased as a function of ${\mathrm{Yb}}^{\text{3+}}$ concentration, the infrared emission decreased in the same manner. The results suggest that the codoping with ${\mathrm{Yb}}^{\text{3+}}$ favors only the upconversion processes which depopulate the ${}^4{I}_{\text{11/2}}$ level, reducing the 2.8 μm emission intensity. On the other hand, the ${\mathrm{Yb}}^{\text{3+}}$ codoping will certainly increase the efficiency of an upconversion based device. Quantum efficiencies of infrared emissions and radiative lifetimes were calculated by using the Judd–Ofelt approximation. ${\mathrm{Er}}^{\text{3+}}–{\mathrm{Er}}^{\text{3+}}$ and ${\mathrm{Er}}^{\text{3+}}–{\mathrm{Yb}}^{\text{3+}}$ energy transfer efficiencies were calculated using the measured lifetimes of the levels involved in the energy transfer processes.

A multiwavelength thermal lens (TL) method was developed to determine the fluorescence quantum efficiency of solids. The experiments have been performed in Nd3+-doped fluoride glasses, using five different excitation wavelengths: 514, 576, 741, 796, and 867 nm. In this work, the absolute value of fluorescence quantum efficiency can be obtained by the linear dependence of the TL signal with the excitation wavelength. Our results suggest that the method can be applied to study a wide range of fluorescent materials, with a special ability to be used for measurements of highly transparent materials with very low TL effect.